PROJECT SUMMARY Transplantation of insulin-secreting beta cells is an effective therapy for Type 1 diabetes (T1D). To secure supplies of these therapeutic cells, many research groups are actively optimizing protocols to derive insulin+ cells by differentiation of human embryonic stem cells (hESCs) or by reprogramming of adult tissues. The next major challenge is to discover methods to protect transplanted cells from autoimmunity to achieve long-term glycemic control. Clinical observations have long suggested existence of beta cells in T1D patients that escape autoimmunity and continue to function. Such cells are very challenging to study from clinical samples. New research tools are needed to address the critical question of how to produce insulin-secreting cells that resist autoimmunity. Our laboratory recently discovered that insulin-secreting cells can be readily produced from murine gastric tissues using a direct reprogramming approach with defined genetic factors Ngn3, Pdx1, and Mafa (referred to as NPM factors). The gastric-derived insulin+ cells share key molecular and functional features of pancreatic beta cells but are not identical to native beta cells. We transplanted gastric insulin+ cells into the NOD murine model of T1D and made the surprising observation that gastric insulin+ cells, unlike native pancreatic beta cells, are not subject to strong immune attack, suggesting reduced immunogenic properties. This observation raised the exciting possibility that gastric-derived insulin+ cells could be employed as a novel tool to study immune-beta cell interactions in human T1D and may be further developed into a transplantation therapy that requires minimal immune protection. In this proposal, we will develop new methods to produce functional insulin-secreting cells from human gastric tissues using two separate approaches and study their immunogenic properties with a variety of tools including human T1D- derived T-cell clones. Our ultimate goal is to gain mechanistic insight into the immune response to beta cells in T1D and to discover novel pathways that may diminish or prevent the autoimmune attack. If successful, this project will also lay the foundation for a novel source of insulin-secreting cells for therapeutic transplantation to treat T1D.